The present invention relates to implantable pacemakers, and more particularly to a connector used by an implantable pacemaker that allows a pacing lead to be detachably, yet reliably, connected to the pacemaker. Even more particularly, the present invention relates to a pacemaker connector made in compliance with precise industry imposed standards, but made in a way that does not require expensive, precision parts, nor a complex assembly or manufacture.
A pacemaker is a medical device that selectively provides stimulation pulses to the heart, or other body tissue, for the purpose of causing a desired muscle contraction. When properly used, a pacemaker can maintain a desired heart rate, causing the heart to beat so as to maintain the efficient flow of blood through a patient's body.
Modern pacemakers are made to be implanted in a patient, typically in a "pocket" of fatty tissue near the patient's upper breast or lower abdomen. As such, the electronic circuits used within a pacemaker are hermetically sealed in a suitable housing, compatible with body tissue. Electrical connection is made with the pacemaker circuits via feedthrough terminals that pass through the hermetically sealed housing. These feedthrough terminals are then electrically connected to a "pacemaker connector", which pacemaker connector is attached to the pacemaker housing. A pacemaker lead is used with an implantable pacemaker in order to maintain electrical contact between a desired tissue location and the pacemaker circuits. For cardiac pacing, such lead is typically inserted through one of the main veins of the patient, e.g., the superior vena cava, so that a distal end of the lead is directed inside of the heart. Electrodes positioned at the distal end of the lead make contact with the cardiac tissue. The proximal end of the pacemaker lead is then connected to the pacemaker connector.
The pacemaker connector typically takes the form of a female connector, with the proximal end of the pacemaker lead taking the form of a male connector. When joined together, good electrical contact must be maintained between a proximal electrode of the pacemaker lead and an appropriate feedthrough terminal of the pacemaker housing. Further, such connection must be secure, so that it does not disconnect during use, yet it must be detachable, in the event the pacemaker or lead needs to be replaced. Moreover, such connections must at all times remain insulated and sealed from body fluids, which body fluids are conductive and could cause an electrical short.
For single conductor pacemaker leads, the pacemaker connector has typically included a connector block having a recess or hole into which a proximal electrode pin of the pacing lead is inserted and secured with a set screw. Suitable means are then used to electrically connect the connector block to the pacemaker's feedthrough terminal. The connector block is then cast into a suitable epoxy "header assembly" that forms the "connector top" portion of the pacemaker. The cast header assembly both insulates the connector block from body fluids, and positions the header block so as to properly receive the proximal electrode of the pacemaker lead. For multi-conductor pacemaker leads, e.g., bipolar pacing leads, one or more proximal ring electrodes of the pacing lead must also make secure electrical contact with an appropriate feedthrough terminal on the pacemaker housing. Numerous schemes have been proposed and used over the years to achieve this purpose, with varying degrees of success. See, e.g., U.S. Pat. No. 4,764,132 (an earlier patent of Applicant's directed to the problem of making a secure electrical connection to the delicate proximal ring electrode of a pacing lead using a set screw without deforming the proximal ring electrode).
Thus, over the approximately 30 year history of implantable pacemakers, a wide variety of techniques and methods have been used to connect leads to pacemakers. Many of these methods and techniques are no longer suitable for the smaller pacemakers and leads that are currently being used.
Recently, an effort has been underway to standardize the interface between a pacemaker lead and a pacemaker. See, e.g., Calfee et al., "A Voluntary Standard for 3.2 mm Unipolar and Bipolar Pacemaker Leads and Connectors," PACE, Vol. 9, 1181-85 (Nov.-Dec. 1986). The standard therein proposed, referred to as the VS-1 (voluntary standard-1), has subsequently been adopted by almost all pacemaker manufacturers worldwide. The VS-1 standard does not specify how a particular pacemaker connector must make contact with a pacemaker lead, it simply defines the dimensions of the pacemaker lead and the dimensions of the pacemaker connector cavity into which the pacemaker lead is inserted. The VS-1 standard further specifies certain requirements as to leakage, conductivity and connection/disconnection force. While the VS-1 standard advantageously represents a long needed movement towards industry standardization, when translated to a particular type of pacemaker connector design, the VS-1 standard disadvantageously sets some rather stringent manufacturing tolerances. Such stringent manufacturing tolerances have heretofore only been obtainable using labor intensive, expensive manufacturing techniques, e.g., machining of individual parts.
What is needed, therefore, is a pacemaker connector that meets the VS-1 standard, and that also can be made using less labor-intensive and less expensive manufacturing methods and techniques. The present invention advantageously addresses this and other needs.